1. Field of the Invention
The present invention relates to a display apparatus having ventilation means capable of cooling the heat generated by causing a luminous element to emit light.
2. Description of the Related Art
Recently, display apparatus using, for example, a cathode ray tube (CRT), an electrical discharge tube or a light-emitting diode element (hereinafter referred to as "LED") is known. Display apparatus using, for example, LEDs is used as large screen display apparatus for the wall of building or outdoor advertisement.
By the way, it is considered that the light-transforming coefficient of, for example, a CRT or electrical discharge tube is, for example, about 10% and that of an LED is, for example, not much exceeding several percent, so that it follows that a majority of the energy is transformed into heat. Since by this heat a change in physical properties such as, for example, a light-emitting property is accelerated, in order to maintain initial performance and ensure reliability for a long period of time, it is desirable to lower the temperature by using some cooling means. Therefore, means for efficiently carrying out cooling have been considered.
For example, as means for cooling the LED, it is a usual method to discharge heat generated by various kinds of circuit elements mounted on an LED mounting substrate to the outside with the aid of thermal conduction of lead terminals of LEDs. Accordingly, effective discharge of heat can be achieved by making the lead terminal thick so as to increase heat discharging surface area.
However, when a display apparatus is installed outdoors, in order to adopt a waterproof structure for preventing water such as rain from entering the LED mounting substrate, it is necessary to mold, for example, lead terminal portions with waterproof resin or the like. When this structure is adopted, since the heat discharging effect of the lead terminals is reduced, it follows that there is no way other than to cool the LED mounting substrate itself. However, when the mounting substrate is cooled, heat at a rear portion of a display unit on which the mounting substrate is arranged has to be discharged to outside. That is, at a rear side of the display apparatus, since it is necessary to provide, for example, a cooling air conditioner, remove heat from the mounting substrate with the cooling air thereof and discharge heated air to outside of the display unit, a structure of the rear portion of the display unit becomes complicated as a result of obtaining this ventilation passage or the like. In particular, when cooling is carried out using a cooling device such as a cooler, etc., since a large cooling device is required for a large display apparatus, there is such a problem that it is difficult to obtain installation space and the cost becomes high.